The problem, particularly in the case of flat cables that have energy transmission and data transmission cores, lies in piercing the data conductor in the shielded cable without the screw coming in contact with the shield (electrically conductive material), while in the process achieving good contact resistance between the end of the contact tip and the conductor and retaining high dielectric strength between shield and conductor.
In the past this object has been attained by means of a contact screw with an end casing of hard insulating material which extends through the cable jacket, the shield, and the core insulation when the conductor is pierced. One disadvantage of this solution is that the force of penetration is transmitted to the insulating material and the shield is drawn toward the conductor, something which disadvantageously reduces the distance between shield and conductor.